The present invention relates to a process for locating an obstacle in relation to a coordinate system moved along with an unmanned, movable and steerable vehicle by means of ultrasonic waves emitted in the direction of travel by transmitters and reflected ultrasonic waves received by sensors when in the presence of an obstacle. According to the received information, steering and/or braking signals are forwarded to the vehicle for the prevention of a collision with the obstacle. Moreover, the invention relates to a system for locating the position of such obstacle.
German Patent 35 18 613 discloses an obstacle detection system for a self-propelled steerable vehicle having on its side pointing in the driving direction a plurality of ultrasonic wave pulse transmitters arranged in a row next to each other. At least one ultrasonic wave receiver is located in the center of the row along with a device for the excitation of the ultrasonic wave transmitter. A reception evaluation device supplies information about an obstacle located in the driving direction and about its present course with respect to the longitudinal axis of the vehicle. This system is distinguished in that only the one receiver is associated with the plurality of transmitters, in that the equal frequency excitation begins at the same time, and in that in a first mode of operation, the transmitters adjacent to the receiver emit a maximum of pulses and the again adjacent transmitters with increasing distance from the receiver emit a decreasing number of pulses. In a second mode of operation, the transmitter at one end of the row emits a maximum number of pulses and the other transmitters emit a decreasing number of pulses with increasing distance from the receiver. In a third mode of operation, the transmitter at the other end of the row emits a maximum number of pulses while the other transmitters emit a decreasing number of pulses with increasing distance from the receiver. A locating system is disclosed in which as a result of deliberately directed ultrasonic waves the center region as well as the two side regions are only scanned at certain sites so that a constant monitoring of the driving space in front of an unmanned vehicle is not possible. In order to obtain a signal, a plurality of ultrasonic pulses must always be omitted. This leads to expensive and not at all error-free monitoring and evaluation.
German OS 30 34 511 discloses an obstacle detector for vehicles which monitors the space in front of a vehicle by means of light signals and whereby as a result of reflection of the beams on obstacles, a timely braking of the vehicle in front of an occurring obstacle is initiated. Error-free monitoring of the space in front of an unmanned vehicle is not possible with this detector.
The state of the art which has become known thusfar does not include any protective measures against foreign influences such as foreign light sources or foreign ultrasonic transmitters which may falsify or nullify the monitoring result. The monitoring of a pulse curve emitted by a plurality of transmitters by one single receiver is also quite expensive. When the single ultrasonic receiver fails, moreover, the entire ultrasonic monitoring device shuts down.